My Porsche cayenne has been stood for three months and now when started the battery generator light comes on when driven over a short distance also the heater fan has stopped working the battery indicator is only showing 12 on the gauge

  • Welcome to Motor Vehicle Maintenance & Repair! Have you used a multimeter on the battery with engine running to see what the output is? What is the battery voltage at rest? The dash gauge can only tell you so much and is very inaccurate (it's this way for any vehicle). I'd suggest the heater fan not working is a separate issue and should be treated as such. – Pᴀᴜʟsᴛᴇʀ2 Jan 8 '19 at 13:50
  • Welcome to the site. My first suggestion would be to plug the car into a battery charger and leave it overnight. You may find that this resolves all of your issues. – Steve Matthews Jan 8 '19 at 13:54

Automotive batteries really don't like being deeply discharged, and since the Cayenne will almost certainly have a noticeable constant drain courtesy of things like the alarm if you've left just left the battery connected for 3 months it's going to be very, very flat and may well have difficulty taking a charge.

You can try and hook the battery up to a decent "smart" charger such as a CTEK MXS but depending upon the age of the battery and whether it's been flatten before etc it's possible that it's sustained permanent damage. If the problems persist after a decent charge then any decent garage should be able to test the battery for you.

  • the battery was disconnected during the three months – Robert Ince Jan 8 '19 at 14:14
  • @RobertInce hmm.. assuming it was in a healthy state at the time of disconnection I'd reasonably expect it to be okay for that length of time then. Perhaps a loss of 15-20% charge (approx). How old is the battery? – motosubatsu Jan 8 '19 at 14:19

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